Higher density recording has been demanded for a magnetic recording medium. As one approach to meeting this demand, it is known to smoothen the surface of the magnetic layer of such a medium.
However, when the surface of the magnetic layer is made smooth, the friction coefficient, which measures the contact between the magnetic layer and a running system while the magnetic recording medium is running, increases. As a result, the magnetic layer tends to become damaged and/or peel off after only a short period of use.
In order to cope with the above problem, it is known to use lubricating agents such as fatty acid esters (e.g., higher fatty acid esters as disclosed in JP-A-50-22603, JP-A-50-153905, JP-B-39-28367 and JP-B-41-18065; unsaturated fatty acid esters as disclosed in JP-A-55-139637; esters of unsaturated fatty acids as disclosed in JP-A-58-164025; fatty acid esters of unsaturated alcohols as disclosed in JP-B-47-12950); silicon compounds as disclosed in U.S. Pat. No. 2,654,681; fatty acids or hydrocarbons. (The term "JP-A" as used herein means "unexamined Japanese patent application", and the term "JP-B" as used herein means "examined Japanese patent publication").
As another approach to improve running durability, it has been suggested and it has been practiced to add abrasive agents (hard particles) into the magnetic layer.
Recently, with the wide development and use of VTRs, and flexible disk drive apparatuses for word processors and personal computers, magnetic recording media have come to be used under a wide range of conditions, such as at low temperatures and at high temperatures and high humidities. Despite this wide range of conditions, the running durability of the magnetic recording medium should be stable and should not fluctuate. However, conventionally known lubricating agents have been insufficient for maintaining the necessary stability.
When abrasive agents are added into a magnetic layer in order to improve the running durability of the magnetic layer, significant effect are not achieved unless a relatively large amount of the abrasive agents is added. However, it has heretofore been difficult to obtain good running durability without sacrificing electromagnetic characteristics and risking premature head wear-out.